login redirects to discussions index but does not log me in

I've been having this problem since I installed it. Sometimes I have to go through sign in like 10 times to get it to finally sign me in. I searched through the forum but didn't find anything on this, sorry if I inadvertently double posted.

There's nothing in the error log or anything out of the ordinary with the session settings. I'm going to upgrade my version of php and see if that has something to do with it. the server still had version 4, I guess we'll see if upgrading to version 5 makes any difference.